Circuit boards supporting a plurality of interconnected electric components to perform a variety of control functions are well known. In many instances, a plurality of such circuit boards are electrically interconnected to form programmable logic controllers (PLCs) that are normally used to control a number of functions in a manufacturing operation. These programmable logic controllers are often of necessity located on the plant floor and thus are subject to considerable abuse.
The circuit boards are made of a non-metallic material and are normally mounted in a sturdy housing. The circuit boards typically have various input/output devices which must be outwardly exposed to permit operator monitoring and/or actuation. For example, circuit boards of this type can have a key switch control, terminal blocks, and a plurality of light emitting diodes (LEDs) that are outwardly exposed through windows formed in the housing wall. The key switch control provides secured operation of the PLC. The terminal blocks are used for field wiring of sensors and actuators. The LEDs provide a visual indication of the operation of the circuit board. In addition, the circuit boards can have communication ports for coupling the circuit boards to other equipment. The communication ports are also exposed through windows formed with the housing wall. Because of the numerous types of circuit boards, it becomes necessary to supply a plurality of modules housings to accommodate the wide variety of the outwardly exposed input/output components.
It is also well known that the circuit boards require frequent replacement when a malfunction occurs. Since a malfunction of necessity shuts down the machine operation, replacement must be made in a minimum amount of time.
The present invention provides a simplified housing construction which easily accommodates the different types of circuit boards and also provides a novel cover which can be opened quickly to gain access to the electrical components on the circuit board.